This is the only episode in Inside No. 9 that doesn't feature Steve Pemberton.
Hector refers to Andras as: "The Goat of Mendes! The Devil himself!" A direct line from the Hammer film "The Devil Rides Out".
Filmed in the same gothic house as Riddle of the Sphinx, Seance Time, Psychoville and Whitechapel.
Helen McCrory and Aimee-Ffion Edwards previously featured together in Peaky Blinders (2013).
The transcript from the Seasons 1 -3 book shows Hector talking to Katy's father on the telephone - thus inferring it is in order - and lying to her father he hasn't seen her.